Output stage control in the event of a fault
A method for implementing a transition from a functioning steering assistance system to a deactivated steering assistance system when a fault occurs, comprising the following steps: establishing the fault of the steering assistance system; establishing that all high-side power switches are functional (first case), or establishing that all low-side power switches are functional (second case); and in the first case: opening all high-side power switches and performing PWM-like control of the low-side power switches; or in the second case: opening all low-side power switches and performing PWM-like control of the high-side power switches.
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The present invention relates to a method for implementing a transition from a functioning steering assistance system to a deactivated steering assistance system when a fault occurs, and to a steering system comprising a control unit for a vehicle.
BACKGROUND OF THE INVENTIONPower steering systems having an electric driving motor are known from the prior art.
SUMMARY OF THE INVENTIONThere can be a variety of reasons which result in the driving motor not being able to supply force for steering assistance. One possibility is that the output stage of the driving motor is defective, and more particularly that a power switch of the output stage is short-circuited.
If there is a defect in the driving motor, or in the control/output stage thereof, the driving motor is disconnected from the output stage so that steering is not blocked by the driving motor. However, such a phase separation results in a sudden increase in the manual torque at the steering wheel of the particular vehicle, whereby the driving comfort is considerably reduced.
Therefore, it is an object is to make a device and a method available which ensure a gradual transition from a low manual torque with a functioning steering assistance system to a higher manual torque upon failure of the steering assistance system when a defect occurs in the driving motor or the output stage thereof.
As a first embodiment of the invention, a method for implementing a transition from a functioning steering assistance system to a deactivated steering assistance system when a fault occurs is made available, comprising the following steps: establishing the fault of the steering assistance system; establishing that all high-side power switches are functional (first case), or establishing that all low-side power switches are functional (second case); and in the first case: opening all high-side power switches and performing PWM-like control of the low-side power switches; or in the second case: opening all low-side power switches and performing PWM-like control of the high-side power switches.
A vehicle may be a passenger car, a truck, an aircraft or watercraft, or an agricultural vehicle, for example.
As a result of switching “off”/deactivating all high-side or all low-side power switches, the power consumption of the driving motor controlled by the particular output stage is limited. In addition, power can dissipate from the driving motor due to the PWM-like control of the remaining power switches. Abrupt deactivation of the steering assistance system is thus prevented, and a gradual transition from a functioning steering assistance system to a deactivated steering assistance system takes place. The manual torque necessary at the steering wheel of the particular vehicle is thus not abruptly increased in the event of a malfunction, and the driving comfort can be ensured even in the event of a fault.
As a second embodiment of the invention, a steering system comprising a control unit for a vehicle is made available, wherein the control unit comprises a memory means having a computer program stored thereon, the computer program being configured to carry out the method.
As a third embodiment of the invention, a computer program for carrying out the method is provided.
As a fourth embodiment of the invention, a computer program product is provided, comprising program code means stored on a computer-readable data medium, so as to carry out the method, if the program code means are executed on a computer.
In one further embodiment according to the invention, a method is made available, wherein, in the first case, not all low-side power switches, and in the second case, not all high-side power switches, are controlled in a PWM-like manner, but in each case one or more power switches are continuously turned on.
An even smoother transition can be achieved by permanently controlling/activating one or more power switches.
It can be considered one idea of the invention to deactivate the high-side or the low-side power switches of the output stage in the event of a fault, and to control the remaining switches permanently or in a PWM-like manner. This results in a gradual deactivation of the steering assistance system, whereby the driving comfort is increased in the event of a fault.
Of course, the individual features can also be combined with each other, whereby advantageous effects may be achieved in some instances, which exceed the sum of the individual effects.
Further details and advantages of the invention will be apparent based on the exemplary embodiments shown in the figures.
It shall be noted that the term “comprise” does not exclude additional elements or method steps; likewise, the term “a” or “one” does not exclude multiple elements and steps.
The reference numerals used are provided merely for the sake of better understanding and shall not be considered to be limiting under any circumstances, the claims reflecting the scope of the invention for which protection is sought.
LIST OF REFERENCE NUMERALS
- 1 critical manual torque
- 2 manual torque without steering assistance (passive)
- 3 peak
- 4 occurrence of a defect/malfunction/fault
- 5 polling for faults of the steering assistance system yes/no
- 6 polling if all high-side power switches are functional yes/no
- 7 process chain of fast clocking of the low-side power switches
- 8 process chain of fast clocking of the high-side power switches
- 11 manual torque with steering assistance (active)
- L1 high-side power switch
- L2 high-side power switch
- L3 high-side power switch
- L4 low-side power switch
- L5 low-side power switch
- L6 low-side power switch
- T1 circuit breaker U phase
- T2 circuit breaker V phase
- T3 circuit breaker W phase
- M driving motor
Claims
1. A method for implementing a peakless transition in required manual torque when transitioning, due to a fault, from a functioning steering assistance system to a deactivated steering assistance system, comprising the following steps:
- establishing the fault of the steering assistance system;
- while occurrence of said fault is established, establishing that all high-side power switches are functional (first case) or establishing that all low-side power switches are functional (second case); and
- while occurrence of said fault is established, dissipating energy from a driving motor of the steering assistance system to achieve a smooth transition without peaks in required manual torque to transition from said functioning steering assistance system to said deactivated steering system by in the first case: opening all high-side power switches and performing PWM-like control of the low-side power switches; or in the second case: opening all low-side power switches and performing PWM-like control of the high-side power switches.
2. The method according to claim 1, wherein, in the first case, not all low-side power switches, and in the second case not all high-side power switches, are controlled in a PWM-like manner, but in each case one or more power switches is continuously turned on.
3. A steering system comprising a control unit for a vehicle, wherein the control unit comprises a memory means having a computer program stored thereon, the computer program being configured to carry out the method according to claim 1.
4. A non-transitory computer-readable storage medium that stores program code means which upon execution by a computer performs the steps for implementing a peakless transition in required manual torque when transitioning, due to a fault, from a functioning steering assistance system to a deactivated steering assistance system, comprising:
- establishing the fault of the steering assistance system;
- while occurrence of said fault is established, establishing that all high-side power switches are functional (first case) or establishing that all low-side power switches are functional (second case); and
- while occurrence of said fault is established, dissipating energy from a driving motor of the steering assistance system to achieve a smooth transition without peaks in required manual torque to transition from said functioning steering assistance system to said deactivated steering system by in the first case: opening all high-side power switches and performing PWM-like control of the low-side power switches; or in the second case: opening all low-side power switches and performing PWM-like control of the high-side power switches.
5. A steering system comprising a control unit for a vehicle, wherein the control unit comprises a memory means having a computer program stored thereon, the computer program being configured to carry out the method according to claim 2.
6. A non-transitory computer-readable storage medium that stores program code means which upon execution by a computer performs the steps for implementing a peakless transition in required manual torque when transitioning, due to a fault, from a functioning steering assistance system to a deactivated steering assistance system, comprising:
- establishing the fault of the steering assistance system;
- while occurrence of said fault is established, establishing that all high-side power switches are functional (first case) or establishing that all low-side power switches are functional (second case); and
- while occurrence of said fault is established, dissipating energy from a driving motor of the steering assistance system to achieve a smooth transition without peaks in required manual torque to transition from said functioning steering assistance system to said deactivated steering system by in the first case: opening all high-side power switches and performing PWM-like control of the low-side power switches; or in the second case: opening all low-side power switches and performing PWM-like control of the high-side power switches; and
- wherein, in the first case, not all low-side power switches, and in the second case not all high-side power switches, are controlled in a PWM-like manner, but in each case one or more power switches is continuously turned on.
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Type: Grant
Filed: Mar 24, 2014
Date of Patent: Jan 17, 2017
Patent Publication Number: 20140309890
Assignee: Robert Bosch Automotive Steering GmbH (Schwaebisch Gmuend)
Inventor: Markus Weber (Goeppingen)
Primary Examiner: Thomas G Black
Assistant Examiner: Peter D Nolan
Application Number: 14/223,049
International Classification: B62D 5/04 (20060101);